content: /*
   * Copyright 2011-2016 David Karnok
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package ix;
  
  import java.util.*;
  
  /**
   * Emits every Nth item from upstream.
   *
   * @param <T> the value type
   */
  final class IxEvery<T> extends IxSource<T, T> {
  
      final int nth;
  
      IxEvery(Iterable<T> source, int nth) {
          super(source);
          this.nth = nth;
      }
  
      @Override
      public Iterator<T> iterator() {
          return new EveryIterator<T>(source.iterator(), nth);
      }
  
      static final class EveryIterator<T> implements Iterator<T> {
  
          final Iterator<T> source;
  
          final int nth;
  
          boolean done;
  
          boolean hasValue;
  
          EveryIterator(Iterator<T> it, int nth) {
              this.source = it;
              this.nth = nth;
          }
  
          @Override
          public boolean hasNext() {
              if (done) {
                  return false;
              }
              if (!hasValue) {
                  int i = nth - 1;
  
                  Iterator<T> src = source;
  
                  while (i != 0 && src.hasNext()) {
                      src.next();
                      i--;
                  }
  
                  if (src.hasNext()) {
                      hasValue = true;
                      return true;
                  }
  
                  done = true;
                  return false;
              }
              return true;
          }
  
          @Override
          public T next() {
              if (hasNext()) {
                  hasValue = false;
                  return source.next();
              }
              throw new NoSuchElementException();
          }
  
          @Override
          public void remove() {
              source.remove();
          }
      }
  }
  